The disclosed invention is generally directed to a head-up virtual image display for aircraft avionic instrumentation, and is directed more particularly to an aircraft instrument display that includes a combiner that is separate from the windshield.
Instrument displays for the primary aircraft avionic instruments are commonly located on an instrument panel located in front of the pilot and co-pilot seats and below the windshield. Secondary instrument displays and annunciators are sometimes located in an overhead panel above the windshield.
Depending on flying conditions, an aircraft pilot can be continually alternating between scanning the outside scene and scanning the aircraft avionic instrument displays, which requires the pilot to divert his or her eyes from the outside to the instruments and back to the outside. Each diversion also requires refocusing of the eyes.
In recognition of the desirability of head-up viewing of avionics instrumentation displays, head-up displays have been utilized in military aircraft to (1) provide the pilot with target information from radar, (2) provide flight instrumentation information such as an artificial horizon or glideslope indicators, and/or (3) produce synthetic land maps for flight in low visibility weather conditions or flight at low altitude above ground level. However, military head-up displays are complex and expensive, typically achieving their intended functions with large fields of view, complex optics, and cathode ray tubes. Moreover, aircraft for commercial and general aviation do not require the capabilities of military head-up displays, which would be particularly expensive for smaller general aviation aircraft.
Head-up displays have also been implemented for automobiles. However, such head-up displays generally utilize the windshield or apparatus attached to the windshield as the combiner element. The use of the windshield as part of the combiner element presents difficulties in the use of coatings for improving the reflected image and preventing ghost images.